WO2005095681A1 - Method for producing iii group element nitride crystal, production apparatus for use therein, and semiconductor element produced thereby - Google Patents

Abstract

A method for producing a III Group element nitride crystal having a crystal growth step of heating under pressure a raw material fluid containing at least one of an alkali metal and an alkaline earth metal, a III Group element and nitrogen in an atmosphere of a gas containing nitrogen, to thereby react the nitrogen and the III Group element in the above raw material fluid and grow crystals, which further comprises a raw material preparation step, prior to the above crystal growth step, wherein nitrogen is dissolved in a melt containing at least one of an alkali metal and an alkaline earth metal in an atmosphere of a gas containing nitrogen under a condition wherein at least one of the temperature and the pressure of the atmosphere is set at a higher level than that for the above crystal growth step, to prepare the above raw material fluid; a production apparatus for practicing the above method, for example, shown in FIG. 7; and a semiconductor element produced by the above. The method allows the production of a crystal of a III Group element nitride having high quality and a large size in a short time, with an improved growth rate.

Description

 Specification

 Method for producing group III element nitride crystal, production apparatus used therefor, and semiconductor element obtained by them

 Technical field

 The present invention relates to a method for producing a group III element nitride crystal, a production apparatus used for the method, and a semiconductor device obtained by the method.

 Background art

 [0002] Gallium nitride (GaN) has attracted attention as a material for semiconductor elements that emit blue or ultraviolet light. Blue laser diodes (LDs) are applied to high-density optical discs and displays, and blue light-emitting diodes (LEDs) are applied to displays and lighting. Ultraviolet LDs are also expected to be applied to biotechnology, etc., and ultraviolet LEDs are expected to be used as ultraviolet light of fluorescent lamps.

[0003] A GaN crystal for LD or LED is usually formed on a sapphire substrate by heteroepitaxially growing a GaN crystal using a vapor phase epitaxy method. The dislocation density of the GaN crystal obtained by this method typically, 10 ⁸ cm- ² ~: for 10 ⁹ cm- is ^2, there is a problem with the quality of the resulting crystals. As a method for solving this problem, for example, an ELOG (Epitaxial lateral overgrowth) method has been developed. According to this method, the dislocation density can be reduced to about 10 ⁵ cm ² to about 10 ⁶ cm ² . However, this method has a problem that the process is complicated.

[0004] On the other hand, a method of performing crystal growth in a liquid phase rather than vapor phase epitaxial growth has been studied. However, since the equilibrium vapor pressure of nitrogen at the melting point of the GaN crystal is more than 10,000 atm (10 000 × 1.013 × 10 ⁵ Pa), 1200 is required for growing the GaN crystal in the liquid phase. C required 8000 atm (8000 X l. 013 x 10 ⁵ Pa), which is the power required for severe conditions. To solve this problem, a method using Na flux has been developed. According to this method, a GaN crystal can be obtained under relatively mild conditions. Further, in a nitrogen gas atmosphere containing ammonia, a mixture of Ga and Na is heated under pressure and melted, and the melt is grown for 96 hours to obtain a maximum crystal size of about 1.2 mm. Thus, a single crystal having a small size has been obtained (for example, see Patent Document 1).

[0005] Further, a method has been proposed in which a reaction vessel and a crystal growth vessel are separated from each other to suppress generation of natural nuclei and grow large crystals (for example, see Patent Document 2).

[0006] However, in the field of Group III element nitrides such as GaN, further improvement in growth rate and quality is required.

 Patent Document 1: JP 2002-293696 A

 Patent Document 2: JP 2003-300798 A

 Disclosure of the invention

 Problems to be solved by the invention

[0007] Therefore, an object of the present invention is to provide a method for producing a Group III element nitride crystal capable of improving a growth rate and growing a large crystal of high quality in a short time, a production apparatus used therefor, and a production apparatus used in the method. To provide a semiconductor device.

 Means for solving the problem

[0008] In order to achieve the above object, the production method of the present invention is a method for producing a solution containing at least one of an alkali metal and an alkaline earth metal, a Group III element, and nitrogen under a nitrogen-containing gas atmosphere. A method for producing a Group III element nitride crystal, comprising a crystal growth step of growing a crystal by reacting nitrogen in the raw material solution with nitrogen in the raw material liquid by heating under pressure, and further comprising, prior to the crystal growth step, A step of preparing at least one of an alkali metal and an alkaline earth metal under a nitrogen-containing gas atmosphere by setting at least one of an atmosphere temperature and an atmosphere pressure higher than the conditions of the crystal growth step. It is characterized in that it is a step of preparing the raw material liquid by dissolving nitrogen in a melt containing one and a group m element.

[0009] The production apparatus of the present invention is an apparatus for producing a m-group element nitride crystal, which includes a heating means, a calo-pressure means, a nitrogen-containing gas supply means, a crystal growth vessel, a raw material preparation vessel, and a raw material transfer means. The crystal growth vessel and the raw material preparation vessel are connected via the raw material transfer means, and the heating means, the pressurizing means, and the nitrogen A gas-containing supply means is arranged, and the heating means, the pressurizing means, and the nitrogen-containing gas supply Step, pressurize and heat under a nitrogen-containing gas atmosphere to prepare a melt containing a Group III element and at least one of an alkali metal and an alkaline earth metal in the raw material preparation vessel, and prepare the melt in the melt. A raw material liquid is prepared by dissolving nitrogen, and the raw material liquid is transferred from the raw material preparation vessel to the crystal growth vessel by the raw material transfer means, and the inside of the crystal growth vessel is heated by the heating means and the heating means. Pressurizing and heating under a nitrogen-containing gas atmosphere by the pressure means and the nitrogen-containing gas supply means to cause the nitrogen in the raw material liquid to react with the group IV element in the crystal growth vessel, and This is an apparatus for growing and manufacturing a product crystal, wherein at least one of the ambient temperature and the atmospheric pressure in the raw material preparation container is set higher than the crystal growth container.

The invention's effect

The present inventors have conducted a series of studies on the growth of Group III nitride crystals. In the process, in the case of the conventional method, there is a long period of time during which no crystal grows at the beginning of crystal growth, and the time that does not contribute to the initial crystal growth depends on the force depending on the crystal growth conditions. It was found that the time was very long, about 48 hours and about 20% to 50% of the total growth time. As described above, the existence of the time that does not contribute to the crystal growth substantially shortens the time during which the crystal grows, and as a result, the thickness of the grown crystal is reduced by the growth time (including the time that does not contribute to the growth). The apparent crystal growth rate divided by In other words, when growing a large crystal or a thick film crystal, the time required to obtain a crystal of a desired size becomes longer. In the course of further research, the present inventors have stated that the cause of the time during which no crystal grows at the beginning of crystal growth is that sufficient time is required for nitrogen to dissolve in the melt containing the group III element. I figured it out. Therefore, based on this finding, the present inventors have further studied and reached the present invention. In other words, prior to crystal growth, by setting at least one of the ambient temperature and the atmospheric pressure higher than the crystal growth conditions in advance, a melt containing at least one of an alkali metal and an alkaline earth metal and a Group III element can be obtained. The raw material liquid is prepared by forcibly dissolving nitrogen in the raw material (raw material preparation step: in this state, the Group III element nitride crystal in the melt (raw material liquid) is saturated or unsaturated). Thereafter, for example, the temperature of the raw material liquid is lowered to a desired temperature, and the state of the group III element nitride crystal in the melt is changed from a saturated or unsaturated state to a supersaturated state. As a result, the crystal is grown at a desired atmosphere temperature and pressure (crystal growth step: in this state, the Group III element nitride crystal in the melt is in a supersaturated state). Alternatively, after the raw material preparation step, the crystal growth is performed by reducing the atmospheric pressure to a desired pressure. In this way, by performing the raw material preparation step, compared with the conventional method in which the temperature and pressure of the atmosphere are maintained at the crystal growth conditions from the stage of dissolving the nitrogen in the melt, the time until the supersaturation is reached is reduced. Can be shortened. Therefore, according to the present invention, it is possible to start the crystal growth of the m-group element nitride crystal in a state where the time not contributing to the growth time is reduced or almost not. When the atmospheric pressure is reduced to a desired pressure, immediately after that, the m-group element nitride crystal in the melt is in a saturated or unsaturated state, but the atmospheric pressure is maintained at the desired pressure for a certain period of time. By holding, the nitrogen is further dissolved in the melt (raw material liquid), and the m-group element nitride crystal in the melt becomes a supersaturated state and crystal growth starts. The dissolution of nitrogen in the melt in the raw material preparation step can be performed in a shorter time by using, for example, an ambient temperature, an ambient pressure, a gas supply method (eg, gas flow and publishing), and ultrasonic waves. Can be done with In the crystal growth step, for example, the m-group element nitride crystal was grown three-dimensionally by keeping the atmospheric pressure and the atmospheric temperature constant during the crystal growth, or by gently changing them. Even in this case, the crystal growth rate can be kept constant. As a result, for example, a high-quality crystal with little change in impurity concentration or the like in the obtained crystal can be grown more quickly.

Brief Description of Drawings

FIG. 1 is a graph showing the relationship between time and ambient temperature in one embodiment of the present invention.

 FIG. 2 is a graph showing a relationship between time and a grown film thickness in the embodiment of the present invention.

 FIG. 3 is a graph showing a relationship between time and atmospheric pressure in another embodiment of the present invention.

FIG. 4 is a graph showing a relationship between time and a grown film thickness in the other embodiment of the present invention. Garden 5] FIG. 5 is a graph showing the relationship between time and ambient temperature in still another embodiment of the present invention.

Garden 6] FIG. 6 is a graph showing the relationship between time and atmospheric pressure in still another embodiment of the present invention.

Garden 7] FIG. 7 is a configuration diagram of a manufacturing apparatus used in the one embodiment of the present invention. Garden 8] FIG. 8 is a configuration diagram of a manufacturing apparatus used in still another embodiment of the present invention.

Garden 9] FIG. 9 is a configuration diagram of a manufacturing apparatus used in still another embodiment of the present invention.

 FIG. 10 is a configuration diagram of a manufacturing apparatus used in still another embodiment of the present invention.

Garden 11] FIG. 11 is a configuration diagram of a manufacturing apparatus used in still another embodiment of the present invention.

 FIG. 12 is a configuration diagram of a manufacturing apparatus used in still another embodiment of the present invention.

 FIG. 13 is a configuration diagram of a manufacturing apparatus used in still another embodiment of the present invention.

 FIG. 14 is a configuration diagram of a manufacturing apparatus used in still another embodiment of the present invention.

 FIG. 15 is a configuration diagram of a manufacturing apparatus used in still another embodiment of the present invention.

 FIG. 16 is a sectional view of a group III element nitride semiconductor device according to an example of the present invention.

Explanation of symbols

 11 Reaction vessel

 12 Raw material preparation container

13 For raw material liquid Crystal growth vessel

 Material preparation container and crystal growth container Material transfer means

 Pipe

, 21 gas supply equipment

 Flow regulator

 Gas inlet pipe

, 26 pressure regulator

 Cap

 Heat barrier

 Ultrasonic generator

, 34 heater for heating

, 48, 49

 Partition board

 Lid

 Seed crystal

 Crystal growth vessel

 Raw material preparation container

 1st pressure vessel

, 53 pressure vessels

 Second pressure vessel

 Drive means

 Rotation introduction means

 Stirring means

 Semiconductor laser

 Substrate

 Contact layer

Cladding layer 94, 96 Light guide layer

 95 Multiple quantum well layer

 97 cladding layer

 98 Contact Layer

 99 Insulation film

 100 p side electrode

 101 n-side electrode

 A Material transfer direction

 B Gas supply direction

 BEST MODE FOR CARRYING OUT THE INVENTION

[0013] As described above, the production method of the present invention is a production method including a raw material preparation step and a crystal growth step. In the raw material preparation step, by setting at least one of the atmospheric temperature and the atmospheric pressure higher than the conditions of the crystal growth step, nitrogen is dissolved in the melt to prepare the raw material liquid (in this state, the melt ( Group III element nitride crystals in the raw material solution) are saturated or unsaturated.) Then, at least one of the atmospheric temperature and the atmospheric pressure is once lowered to bring the Group III element nitride crystal in the raw material liquid into a supersaturated state, and the Group III element nitride crystal is grown in the raw material liquid. When only the ambient temperature is lowered, this operation alone can quickly bring the Group III element nitride crystal in the raw material solution into a supersaturated state, greatly shortening the time not contributing to crystal growth, and starting crystal growth. You can start. When only the atmospheric pressure is decreased, the Group III element nitride crystal in the raw material liquid immediately thereafter is in a saturated or unsaturated state. By maintaining this pressure for a certain period of time while applying pressure, nitrogen is further dissolved in the raw material liquid, and the material grows into a supersaturated state and crystal growth starts. It can be performed. In this case, the crystal can be grown at a higher ambient temperature than in the case where only the ambient temperature is lowered, and as a result, the crystal can be grown under the condition that the impurity is less taken up. Further, the m-group element nitride crystal in the raw material liquid may be supersaturated by simultaneously lowering the atmospheric pressure and the atmospheric temperature to grow the crystal.

[0014] The ambient temperature in the present invention is, for example, 800 ° C to 1 ° C in the raw material preparation step. It is in the range of 100 ° C, preferably 850. When the temperature is in the range of C to 1000 ° C., the evaporation of the alkali metal and the alkaline earth metal can be suppressed, and the group III element nitride crystal can be efficiently dissolved. In the crystal growth step, for example, the temperature is in the range of 600 ° C. to: 1000 ° C., preferably 800 ° C. to 950 ° C. The difference between the ambient temperatures in the raw material preparation step and the crystal growth step is, for example, 20 ° C to 200 ° C, and preferably 50 ° C to 100 ° C.

[0015] atmospheric pressure in the present invention, in the raw material preparation step, for example, 2atm~10 0atm: in the range of ^{(2 X l 013 X 10 5} Pa~. 100 X 1. 013 X 10 5 Pa), preferably is 10a a tm~70atm (10 X l. 013 X 10 5 Pa~70 X 1. 013 X 10 5 Pa), with such a pressure range, suppress evaporation of alkali metals and alkaline earth metals A group III element nitride crystal can be efficiently dissolved using a relatively inexpensive pressure vessel. The crystal growth step is performed in the range of 2 atm to 100 atm (2 X l. 013 X 10 ⁵ Pa to: 100 X 1.03 X 10 ⁵ Pa), preferably 25 atm. a ~50atm (25 X 1. 013 X 10 5 Pa~50 XI. 013 X 10 5 Pa). The difference between atmosphere pressure of the raw material preparation step and the crystal growth step, for example, 0 · latm~30atm (0. 1 X 1. 013 X 10 5 Pa~30 X 1. 0 13 X 10 5 Pa) by weight, preferably 0. 5atm~20atm (0. 5 X 1. 013 X 10 5 Pa~20 X 1. 013 X 10 5 Pa).

 [0016] In the present invention, when the atmosphere temperature is changed during the crystal growth step, after switching from the raw material preparation step to the crystal growth step, the atmosphere temperature in the crystal growth step is gradually lowered to obtain a predetermined crystal. It is preferable to set the growth temperature. The decrease in the ambient temperature may be, for example, continuous or stepwise. Examples of a method of gradually lowering the ambient temperature include, for example, a method of once lowering the ambient temperature, maintaining the temperature for a certain period of time, lowering the temperature again, repeating these steps, or changing the rate of decrease. Method and the like. When changing the descending speed, the descending speed may be changed to two stages or to more stages. The rate of decrease in the ambient temperature is, for example, 0.05 ° C / hour to 30 ° C / hour, preferably 0.1 ° C / hour to 5 ° C / hour, and more preferably 0.1 ° C / hour. C / hour to 1 ° C / hour.

In the present invention, when the atmospheric pressure is changed during the crystal growth step, the above-mentioned raw material preparation is performed. After switching from the manufacturing process to the crystal growth process, it is preferable to gradually increase the atmospheric pressure in the crystal growth process to a predetermined crystal growth pressure. The increase in the atmospheric pressure may be, for example, continuous or stepwise. When the atmospheric pressure is increased stepwise, for example, once the atmospheric pressure is increased, the temperature is maintained for a certain period of time, then the pressure is increased again, and a method of repeating these steps or changing the rate of increase are used. Method and the like. When changing the rising speed, the rising speed may be changed in two stages or may be changed in more stages. Further, the decrease in the atmospheric temperature and the increase in the atmospheric pressure may be performed independently or simultaneously. The atmosphere increases the rate of pressure, for example, 0. Olatm / Time ~ 0 · 3 atm / Time (0. 01 X 1. 01 3 X 10 5 Pa / Time ~ 0. 3 X 1. 013 X 10 5 Pa / and time), preferably 0 · 05atm / time ~ 0. LATM / time (0. 05 X 1. 013 X 10 5 Pa / time ~ 0. 1 X 1. 013 X 10 5 Pa / hour).

 As described above, by gradually lowering the ambient temperature or gradually increasing the atmospheric pressure during the crystal growth, the substantial crystal growth rate can be further increased. Further, by performing both of these at the same time, the crystal growth rate can be further increased. In the present invention, the substantial crystal growth rate is, for example, 5 × m / hour to 100 × m / hour, and preferably 10 × m / hour to 50 × m / hour. The substantial crystal growth rate in the present invention means the thickness of a crystal grown per hour from when crystal growth actually starts to when it ends (excluding time that does not contribute to crystal growth). .

In the crystal growth step, the rate of decrease in the ambient temperature and the rate of increase in the ambient pressure may be constant or may be varied. For example, during the middle to late stages of crystal growth, the rate of decrease in the ambient temperature and the rate of increase in the ambient pressure may be gradually increased. By making such a change, even when the crystal shape becomes three-dimensionally large, the crystal growth rate in a certain axis (for example, C-axis) direction is almost constant (that is, the group III element nitride in the melt is not changed). The supersaturation degree of the crystal is kept almost constant), and the crystal quality can be made the same at the start of crystal growth and at the latter stage of crystal growth. When the ambient temperature is changed, for example, it is preferable that the temperature be lowered at a rate of 0.05 ° C./hour in the initial stage of crystal growth and 3 ° C./hour in the latter period, and more preferable that the temperature be lowered. Initially 0. C Per hour, and in the latter period as 1 ° C / hour. When the atmospheric pressure is changed, for example, the pressure is increased at 0.1 Olatm / hour (0.01 × 1.013 × 10 ⁵ Pa / hour) in the early stage of crystal growth, and is increased to 0.3 atm / hour (0%) in the latter period. . 3 X 1. 013 X l. 5 Pa / more preferably it is preferred instrument to increase in time between), the initial crystal growth 0. 05atm / inter hr (0. 05 X 1. 013 X 10 5 Pa / Hour), and in the latter period, it is increased by 0. latm / hour (0.1 × 1.013 × 10 ⁵ Pa / hour).

 In the raw material preparation step of the present invention, it is preferable that the raw material liquid is in a state of being saturated or unsaturated with the group III element nitride crystal. The unsaturated state means a state in which the dissolution of the group III element nitride crystal in the raw material liquid is still possible. The solubility of the group III element nitride in the raw material liquid is, for example, 0.2 to 5 at.%, Preferably 0.2 at.% To lat.%, And the nitrogen concentration in the raw material liquid is % Is, for example, 0.2 Olat.% To 5 at.%, Preferably 0.2 at.% To: lat.%.

 In the raw material preparation step of the present invention, it is preferable to supply the nitrogen-containing gas by flowing the nitrogen-containing gas on the liquid surface of the melt (raw material liquid). The flow can be performed, for example, by supplying the nitrogen-containing gas to the liquid surface of the melt. Further, the flow rate of the nitrogen-containing gas to be flown can be controlled by, for example, a mass flow controller or a flow meter.

In the raw material preparation step of the present invention, it is preferable to supply the nitrogen-containing gas by publishing the nitrogen-containing gas in the melt. This is because, by publishing, the gas-liquid interface area where the melt and the nitrogen-containing gas come into contact with each other is increased, and the efficiency of dissolving nitrogen in the melt can be further improved. Further, convection by publishing can, for example, make the nitrogen concentration in the melt uniform. The publishing can be performed, for example, by directly supplying a nitrogen-containing gas into the melt. The flow rate of the nitrogen-containing gas to be bubbled can be controlled by, for example, a mass flow controller, a flow meter, or the like, as in the case of flowing the nitrogen-containing gas. The size of the bubbles supplied by the publishing is not particularly limited, but is preferably as small as possible. For example, microbubbles (eg, a diameter of 100 × m or less) and nanobubbles (eg, a diameter of 100 nm or less) are preferable. Masure, By reducing the bubble in this way, the gas-liquid boundary area where the melt and the nitrogen-containing gas come into contact with each other is further reduced. The number of layers increases, the efficiency of dissolving nitrogen in the melt is improved, and the evaporation of alkali metals and the like in the melt can be suppressed. Further, it is preferable to apply ultrasonic waves to the melt in addition to the publishing. As a result, the bubble force of the nitrogen-containing gas supplied by the publishing is fixed at the position of the node of the ultrasonic wave, for example, so that the bubble can stay in the melt for a longer time and the bubble diameter can be further reduced. Therefore, the dissolving efficiency of nitrogen can be further improved. As a method for obtaining a Group III element nitride crystal by bubbling ammonia gas in a melt containing a Group m element, for example, JP-A-10-7496 and US Pat. No. 6,066,205 Is disclosed. However, in these methods, heterogeneous nuclei are generated or heterogeneous nuclei are incorporated as impurities in the grown crystals because the nitrogen-containing gas is bubbled in the supersaturated melt of the group III nitride crystal. There was a problem. However, in the present invention, such a problem does not occur because the group III element nitride crystal publishes the nitrogen-containing gas in the melt in a saturated or unsaturated state. You get it.

 In the present invention, the raw material preparation step may be performed before or during the crystal growth step and / or during or after the crystal growth step. It is preferable that crystal growth be performed continuously, for example, by simultaneously performing the above. For example, a crystal growth step may be performed by separately preparing a melt (raw material liquid) in which nitrogen is dissolved, and adding it as appropriate. In addition, by continuously performing the raw material preparation step at the time of taking out the crystal, preparing the crystal, and the like, the crystal can be continuously grown thereafter, and the production efficiency can be further improved.

In the present invention, examples of the alkali metal include sodium (Na), lithium (Li), potassium (K), rubidium (Rb), and cesium (Cs). a). These may be used alone or in combination of two or more. Examples of the alkaline earth metal include calcium (Ca), magnesium (Mg), beryllium (Be), strontium (Sr) and barium (Ba), and preferably calcium (Ca) and strontium (Sr). And barium (Ba), and more preferably calcium (Ca). These may be used alone or in combination of two or more. In the present invention, the alkaline earth metals are calcium (Ca), magnesium (Mg), beryllium (Be ), Strontium (Sr) and barium (Ba). In the present invention, the melt may contain, for example, n-type and p-type dopants such as silicon (Si), zinc (Zn) and magnesium (Mg) as dopants.

 [0025] In the present invention, it is more preferable that the GaN crystal is produced using Ga, among which the group IV element is preferably Al, Ga and In.

 [0026] In the present invention, the nitrogen source of nitrogen contained in the raw material liquid is not particularly limited, and may be, for example, a nitrogen-containing gas, a nitrogen compound mixed in the raw material liquid, or the like. Examples of the nitrogen-containing gas (reaction gas) include a nitrogen (N) gas and an ammonia gas), and either one of them may be used, or a mixture thereof may be used. The nitrogen-containing gas (reaction gas) may include, for example, an inert gas (eg, Ar, He and Ne), a hydrogen gas, and the like. Hydrazine (H NNH) may be used as the nitrogen-containing gas (reaction gas) source, or hydrazine may be mixed into the melt and used as a nitrogen source. When hydrazine is used as a nitrogen-containing gas (reaction gas) source, hydrazine decomposes into ammonia and nitrogen at 180 ° C in air. For example, a gas obtained by heating hydrazine can be used as it is as a nitrogen-containing gas. Or diluted with a carrier gas such as nitrogen (N) gas and the above-mentioned inert gas. Also

In the present invention, a pressurized gas for pressurization may be supplied separately from the reaction gas. Examples of the pressurized gas in this case include the above-mentioned inert gas. The pressurized gas may be supplied as a mixture with the reaction gas, or may be supplied independently in a separate system.

[0027] In the present invention, in the crystal growth step, a crystal growth reaction is performed in a crystal growth vessel, and in the raw material preparation step, at least one of the alkali metal and the alkaline earth metal is contained in the raw material preparation vessel. Preferably, nitrogen is dissolved in a melt containing a Group III element to prepare a raw material liquid, and the raw material liquid is transferred from the raw material preparation container to the crystal growth container, where the crystal is grown. The raw material preparation container and the crystal growth container may be separated, or may be integrated. In the case of an integrated container, for example, a raw material preparation container portion and a crystal growth container portion are provided in one reaction container, and the raw material preparation container portion and the crystal growth container portion communicate with each other to form a raw material preparation container. Containers that can transfer the raw material liquid in the container section to the crystal growth container section can be used. In this case, the transfer of the raw material liquid is simplified. There is a sign. When the raw material preparation container and the crystal growth container are separated and arranged in separate pressure vessels, the raw materials are prepared before and after crystal growth (for example, at the time of crystal removal, crystal preparation, etc.). Therefore, the production efficiency can be further improved. In this case, the number of the raw material preparation containers is not particularly limited, and may be one or more. It is preferable to use a plurality of raw material preparation containers. When a plurality of raw material preparation containers are used, the raw material liquid obtained by dissolving nitrogen in the plurality of raw material preparation containers is once collected in another container via a pipe or the like, and then transferred to a crystal growth container. Transport is preferred. The material used for the raw material preparation container and the crystal growth container is not particularly limited.For example, BN, A1N, anolemina, SiC, and carbonaceous materials such as graphite and diamond-like carbon can be used, and are preferable. Is alumina.

Next, as described above, the production apparatus of the present invention is an apparatus for producing a group III element nitride crystal, and includes a heating means, a pressurizing means, a nitrogen-containing gas supply means, a crystal growth vessel, a raw material preparation vessel, and a raw material. A transfer means, wherein the crystal growth vessel and the raw material preparation vessel are connected via the raw material transfer means, and the crystal growth vessel and the raw material preparation vessel are respectively provided with the heating means, the pressurizing means, The nitrogen-containing gas supply means is provided. The heating unit, the pressurizing unit, and the nitrogen-containing gas supply unit set at least one of the atmospheric temperature and the atmospheric pressure in the raw material preparation container higher than that of the crystal growth container under a nitrogen-containing gas atmosphere. Then, the raw material preparation container is heated under pressure to prepare a melt containing at least one of an alkali metal and an alkaline earth metal and a Group III element, and dissolve nitrogen in the melt to obtain a raw material liquid. Is prepared. The raw material liquid is transferred from the raw material preparation vessel to the crystal growth vessel by the raw material transfer means, and the inside of the crystal growth vessel is nitrogen-containing by the heating means, the pressurizing means, and the nitrogen-containing gas supply means. It is manufactured by heating under pressure in a gas atmosphere to cause the nitrogen in the raw material liquid to react with the group III element to grow a group III element nitride crystal. Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-300798) discloses an apparatus in which a crystal growth region and a mixed melt holding region are separated from each other, and the mixed melt holding region has an inert gas atmosphere. Forming a mixed melt of a group III element and an alkali metal under air, and producing a group III element nitride crystal from the mixed melt under a nitrogen atmosphere in the crystal growth region. Has been. Since the mixed melt holding region is under an inert gas atmosphere and does not contain a nitrogen-containing gas, the obtained mixed melt does not contain nitrogen. Therefore, when the apparatus described in the document is used, in the crystal growth region, after dissolving nitrogen in the mixed melt, a Group III element nitride crystal is grown, and no crystal grows in the crystal growth region. Time will exist for a long time. On the other hand, according to the production apparatus of the present invention, in the raw material preparation container, the melt in which nitrogen is dissolved is transferred to the crystal growth container by the raw material transfer means, thereby contributing to crystal growth in the crystal growth container. This significantly reduces the time spent not performing. As a result, the apparent crystal growth rate can be further increased.

 [0029] When the raw material preparation container and the crystal growth container are separated, for example, the first pressure container and the second pressure container are separated.

 And an example in which the first pressure vessel has the crystal growth vessel disposed therein, and the second pressure vessel has the material preparation vessel disposed therein. In this way, by arranging the crystal growth vessel and the raw material preparation vessel in separate pressure vessels, it is possible to prepare the raw material before and after crystal growth (for example, at the time of crystal removal, crystal preparation, etc.). Thus, in addition to the reduction of time that does not contribute to crystal growth, the manufacturing efficiency can be further improved.

 [0030] In the manufacturing apparatus of the present invention, for example, a resistance heater, an RF heater, or the like can be used as the heating means, and the pressurizing means includes, for example, means for pressurizing with a nitrogen-containing gas. is there. In addition, for example, only N gas is used for nitrogen-containing gas (reaction gas) and pressurized gas.

 2

 When used, a gas purification device may be arranged in the gas system. It is preferable that at least one of a temperature adjusting unit and a pressure adjusting unit is further arranged on the device. Thus, for example, the temperature and pressure of the raw material preparation vessel and the crystal growth vessel can be controlled by controlling the heating means or the pressurizing means.

[0031] In the production apparatus of the present invention, as a method of transferring the melt (raw material liquid) in which nitrogen is dissolved from the raw material preparation container to the crystal growth container by the raw material transfer means, for example, A method in which the atmospheric pressure of the pressure vessel is slightly higher than the atmospheric pressure of the first pressure vessel, and transfer using a pump. As the raw material transfer means, for example, a pipe made of metal such as W or Ta, a pipe whose inner wall is coated with BN, SiC, or the like is used. it can. In the raw material transfer means, generation of heterogeneous nuclei can be prevented even when the raw material is transferred, by setting the group III element nitride crystal in the raw material liquid to a saturated or unsaturated state.

 [0032] The manufacturing apparatus of the present invention preferably further includes a gas flow means. This makes it possible to flow the nitrogen-containing gas on the surface of the melt in the raw material preparation vessel, thereby further improving the rate of dissolving nitrogen in the melt. The gas flow means includes, for example, means for supplying the nitrogen-containing gas to the surface of the melt.

 [0033] In the manufacturing apparatus of the present invention, the number of raw material preparation containers is not particularly limited, and may be one or more. It is preferable to use a plurality of raw material preparation containers. . Thereby, the gas-liquid interface area where the melt in the raw material preparation container and the nitrogen-containing gas come into contact can be increased. When a plurality of raw material preparation containers are used, for example, a container for raw materials and the like is provided, and a raw material liquid obtained by dissolving nitrogen in the plurality of raw material preparation containers is supplied to the raw material via a noive or the like. It is preferable to collect it immediately and transfer it to a crystal growth vessel. The material used for the raw material preparation container, the crystal growth container and the raw material is not particularly limited, but examples thereof include BN, A1N, alumina, SiC, and carbon-based materials such as graphite and diamond-like carbon. Materials can be used, preferably anolemina.

[0034] In the production apparatus of the present invention, it is preferable that a gas publishing unit is provided in addition to the gas flow unit or in place of the gas flow unit. This makes it possible to publish the nitrogen-containing gas in the melt in the raw material preparation container, and the nitrogen dissolution rate in the melt can be further improved. Examples of the gas publishing unit include a unit that supplies a nitrogen-containing gas into the melt. By publishing, the area of the gas-liquid interface where the melt and the nitrogen-containing gas come into contact with each other can be increased, and the efficiency of dissolving nitrogen in the melt can be further improved. This is because the nitrogen concentration can be made uniform. The publishing can be performed, for example, by supplying a nitrogen-containing gas into the melt. The flow rate of the nitrogen-containing gas to be bubbled can be controlled by, for example, a mass flow controller or a flow meter in the same manner as in the case of flowing the nitrogen-containing gas. The size of the bubble supplied by the publishing is not particularly limited, For example, microbubbles (for example, a diameter of 100 zm or less) and nanobubbles (for example, a diameter of 100 nm or less) are preferable. By reducing the size of the bubbles in this way, the gas-liquid interface area where the melt and the nitrogen-containing gas come into contact increases, the efficiency of dissolving nitrogen in the melt improves, and the evaporation of alkali metals and the like in the melt increases. Can be suppressed. Further, it is preferable to apply ultrasonic waves to the melt in addition to the publishing. As a result, the bubble of the nitrogen-containing gas supplied by the publishing is fixed, for example, at the position of the node of the ultrasonic wave, so that the bubble can stay in the melt for a longer time or the bubble diameter can be reduced. Therefore, the dissolution efficiency of nitrogen can be further improved.

 [0035] The semiconductor element of the present invention includes the crystal obtained by the above-described manufacturing method.

 [0036] Preferably, the semiconductor element is, for example, a light emitting device such as an LED or a semiconductor laser, or an electronic device such as a power device or a high-frequency amplifier.

 [0037] The manufacturing method and apparatus of the present invention will be described using the following embodiments.

 (Embodiment 1)

 In the present embodiment, a GaN crystal is grown using Ga as a group III element, metal Na as an alkali metal, and nitrogen (N) gas as a nitrogen-containing gas. In that way

 2

 This will be described with reference to FIG. FIG. 7 is a configuration diagram showing an example of a configuration of an apparatus used in the manufacturing method of the present invention. As shown in the figure, this device has a pressure vessel 51, a gas supply device 21, a flow control vessel 22 and a pressure regulator 24 as main components, and the reaction vessel 11 can be accommodated in the pressure vessel 51. A heater 30 for heating is arranged on the side surface. A flow regulator 22 and a pressure regulator 24 are connected to the pressure vessel 51 via pipes, respectively, and the other end of the flow regulator 22 is connected to a gas supply device 21 via a S pipe. Te, ru.

First, Ga and Na are placed in the reaction vessel 11. Then, by using the heater 30 for heating and the pressure regulator 24, the ambient temperature in the pressure vessel 51 is increased from 900 ° C to: 1050 ° C (for example, a temperature higher by 50 ° C to 200 ° C than the crystal growth process), At an atmospheric pressure of 40 atm (40 X 10 .13 X 10 ⁵ Pa), nitrogen is rapidly dissolved in the melt containing Na and Ga, and the nitrogen concentration in the melt is adjusted to a desired nitrogen concentration (the raw material preparation step). ). The amount of nitrogen supply in the pressure vessel 51 is adjusted using the flow rate regulator 22. Then, the atmospheric pressure in the pressure vessel 51 is reduced to 40 atm (40 X 1.013 X 10 ⁵ Pa), the ambient temperature is lowered to 850 ° C, and a GaN crystal is grown in the melt (crystal growth step). As a result, the time from the start of the heating of the raw material to the start of the crystal growth is greatly reduced to, for example, 10 to 30 hours, which is about 1/5 to 1/2 times of the conventional method. FIG. 1 shows an example of a temporal change in the ambient temperature in this embodiment, and FIG. 2 shows an example of the relationship between the growth film thickness and the time. FIG. 2 also shows the relationship between the growth film thickness and time when the crystal was grown by the conventional method. Further, the apparent growth rate is, for example, 15 xm / hour, which can be about 1.5 times faster than the conventional method.

(Embodiment 2)

 In the present embodiment, a GaN crystal is grown using Ga as a group III element, metal Na as an alkali metal, and nitrogen (N) gas as a nitrogen-containing gas. First, the atmosphere

 2

The vapor pressure 60atm~70atm than (60 X l. 013 X 10 5 Pa~70 X 1. 013 X 10 5 Pa) ( ambient pressure in the crystal growth, for example, 20atm~30atm (20 X l. 013 X 10 ⁵ Pa ~ 30 X 1.013 X 10 ⁵ Pa) High pressure), hold the atmosphere temperature at 850 ° C for 1 hour to 5 hours, rapidly dissolve nitrogen in the melt containing Ga and Na, Adjust the nitrogen concentration in the liquid to the desired nitrogen concentration (raw material preparation step). Then, while maintaining the ambient temperature at 850 ° C., the atmospheric pressure is reduced to 40 atm (40 × 10 13 × 10 ⁵ Pa), and the GaN crystal is grown in the melt (crystal growth step). ). As a result, the time from the start of the heating of the raw material to the start of the crystal growth is, for example, 10 to 20 hours, which is drastically reduced from 1Z5 times to 1/2 times of the conventional method. FIG. 3 shows an example of a temporal change in the atmospheric pressure in the present embodiment. Also, the apparent growth rate can be, for example, 15 xm / hour. It should be noted that, as the raw material preparation E Te (Nobi Rere, H i ± ^ ¾r60atm ~ 70atm (60 X 1. 013 X 10 5 Pa~70 X 1. 013 X 10 5 Pa), when the ambient temperature was 850 ° C However, in the equilibrium state, the nitrogen is supersaturated, however, if the nitrogen supply time is as short as 1 hour to 5 hours, for example, the concentration of the group III element nitride (nitrogen concentration) in the melt becomes the saturation concentration. Because of the following, crystal growth does not start in the raw material preparation step.

(Embodiment 3)

In this embodiment, first, a raw material preparation step is performed in the same manner as in Embodiment 1, and the ambient temperature is reduced. After the temperature is lowered, the ambient temperature is further lowered at 0.2 ° C./hour to 1.5 ° C./hour in the crystal growth step. As a result, the substantial crystal growth rate becomes faster, for example, 25 xm / hour. FIG. 5 shows an example of the change over time of the ambient temperature in this embodiment, and FIG. 4 shows an example of the relationship between the growth film thickness and the time. FIG. 4 also shows the relationship between the growth film thickness and the time when the crystal was grown by the conventional method. In the method of lowering the ambient temperature, the temperature does not need to be lowered linearly with time, but may be lowered stepwise. Further, the descending speed may be gradually increased in a range of, for example, 0.1 ° C./hour to 1.5 ° C./hour.

(Embodiment 4)

In the present embodiment, first, a raw material preparation step is performed in the same manner as in the second embodiment, and after reducing the atmospheric pressure, in the crystal growth step, 0.05 atm / hour to 0.3 atm / hour (0.05 X1. 013 X 10 ⁵ Pa / hour to 0.3 X 1.03 X 10 ⁵ Pa / hour). As a result, the substantial crystal growth rate can be higher, for example, 20 / m / hour. FIG. 6 shows an example of a temporal change of the atmospheric pressure in the present embodiment. In addition, the method of increasing the atmospheric pressure may be increased stepwise, especially when it is not necessary to increase the pressure linearly with time. Moreover, the increasing speed, for example, 0. 05atm / Time ~ 0. 3 atm / Time (0. 05 X 1. 013 X 10 5 Pa / H # ^ ~ 0. 3 X 1. 013 X 10 5 Pa / Time ) May be gradually increased.

 Note that Embodiments 1 to 4 do not necessarily need to be performed separately. For example, in the raw material preparation step, by simultaneously increasing the atmospheric temperature and the atmospheric pressure, the melting point in the melt can be improved more efficiently. Can be dissolved in nitrogen.

 Further, in the crystal growth step, by simultaneously lowering the ambient temperature and increasing the atmospheric pressure, the crystal growth rate can be further increased. In the middle to late stages of crystal growth, the rate of increase in the atmospheric pressure may be gradually increased. For example, when the crystal is bulky, the crystal grows three-dimensionally, and as described above, the driving force for crystal growth is increased by gradually increasing the rate of increase in the atmospheric pressure during the middle to late stages of crystal growth as described above. (Supersaturation) can be kept constant, and the growth rate in one crystal axis direction can be kept constant.

(Embodiment 5) An example of the configuration of the manufacturing apparatus of the present invention will be described with reference to FIG. FIG. 8 shows an example of the manufacturing apparatus of the present invention. As shown in the figure, this apparatus comprises a first pressure vessel 50, a second pressure vessel 52, a raw material transfer means 16, pressure regulators 24 and 26, a flow regulator 22, and gas supply devices 21 and 20. Is the main component. In the first pressure vessel 50 and the second pressure vessel 52, a crystal growth vessel 14 and a raw material preparation vessel 12 can be stored, respectively, and the sides of those vessels (14 and 12) are used for heating. A heater 30 is provided. The first pressure vessel 50 and the second pressure vessel 52 are connected by the raw material transfer means 16, and the raw material transfer means 16 is provided with a heater 34 for heating. The gas supply device 20 and the pressure regulator 26 are connected to the first pressure vessel 50 via pipes, respectively.The second pressure vessel 52 has the gas supply device 21, the flow regulator 22, and the pressure regulator. 24 are connected via pipes, respectively.

As the raw material transfer means 16, for example, it is preferable to use a pipe made of a material hardly reacting with Na or a group III element, and specific examples thereof include metal pipes such as W and Ta, BN and Examples include a pipe whose inner wall is coated with SiC or the like. Although the raw material preparation container and the crystal growth container are spatially separated from each other in the figure, the configuration of the production apparatus of the present invention is not limited to this. May be arranged in another place in the same growth furnace, or these vessels may be integrated. By integrating these containers, the power of the raw material preparation container can be further enhanced to facilitate the transfer of the raw material to the crystal growth container.

 [0047] Regarding the production of a group III element nitride crystal using the production apparatus shown in Fig. 8, Ga was used as the group III element, Na was used as the alkali metal, and nitrogen (N) gas was used as the nitrogen-containing gas. A description will be given of an example in which the device is used.

First, Ga and Na in desired amounts are placed in the crystal growth vessel 14 in advance. The nitrogen-containing gas is supplied from the gas supply device 20 to the pressure regulator 26, adjusted to a desired pressure by the pressure regulator 26, and introduced into the first pressure vessel 50. Then, the atmosphere temperature of the first pressure vessel 50 is set to a temperature higher than that of the crystal growth step, for example, 900 ° C. to: 1050 ° C., and the atmosphere pressure is set to 40 atm (40 × 1.013 × 10 ⁵ Pa). A melt is prepared by dissolving the Ga and Na, and nitrogen is dissolved in the melt (raw material preparation step). At this time, the melt in the crystal growth vessel 14 is Nitrogen is dissolved, but GaN is unsaturated. Note that the melt in which the nitrogen is sufficiently dissolved may be prepared in advance in the raw material preparation container 12 and transferred to the crystal growth container 14 using the raw material transfer means 16 for use.

 Next, the ambient temperature of the first pressure vessel 50 is set to 800 ° C., and the ambient pressure is set to 30 atm (30 X 1.

013 × 10 ⁵ Pa) to grow crystals in the melt (crystal growth step). In this case, 900 ° C to ambient temperature of the second pressure vessel 52, an atmosphere pressure 30. latm~31atm (30. 1 X 1. 013 X 10 5 Pa~31 X l. 013 X 10 5 Pa) That's what you like. Further, in order to transfer the melt in the raw material preparation vessel 12 in which nitrogen has been dissolved, the atmospheric pressure of the second pressure vessel 52 is made slightly higher than the atmospheric pressure of the first pressure vessel 50. Is preferred.

 FIG. 9 shows an example of the configuration inside the pressure vessel 52. As shown in the figure, a raw material preparation container 12 is disposed in a second pressure container 52, and a heating heater 30 is disposed on a side surface thereof. A stirring means 74 is attached to the pressure vessel 52 so as to penetrate an upper wall surface thereof, and a driving means 72 is disposed at one end of the stirring means 74 via a rotation introducing means 76. The other end of the stirring means 74 can be arranged in the melt in the raw material preparation container 12, and by driving the stirring means 74 through the driving means 72 and the rotation introducing means 76, The melt in the raw material preparation container 12 can be stirred. In the raw material preparation vessel 12, a gas introduction pipe 23 and a raw material transfer means 16 are arranged, and the melt in which nitrogen is dissolved (raw material liquid) is converted into a crystal growth vessel (not shown) by the raw material transfer means 16. (Arrow A direction). A gas supply device 21 is disposed at one end of the gas introduction pipe 23 via a flow rate regulator 22. Since nitrogen diffuses from the melt surface, the nitrogen concentration on the melt surface (gas-liquid interface) tends to increase. By stirring the raw material liquid in the raw material preparation container with a stirring means such as a propeller, the nitrogen concentration of the raw material liquid in the raw material preparation container can be made more uniform. The propeller material is not particularly limited as long as it does not dissolve in the raw material melt, and examples thereof include tungsten, tantalum, alumina, and yttria. In addition, since the raw material preparation container is set to the saturated or unsaturated atmosphere temperature and the atmospheric pressure, non-uniform nuclei are not generated by stirring.

 FIG. 10 shows another example of the configuration inside the second pressure vessel 52. As shown in FIG.

In the second pressure vessel 52, a plurality of raw material preparation vessels 12 are arranged, and a heating Heater 30 is arranged. Each raw material preparation container 12 is provided with a gas introduction pipe 23 and a pipe 17, and a distal end of the pipe 17 is provided with a raw material liquid 13. A raw material transfer means 16 is disposed in the raw material liquid 13, and the melt (raw material liquid) in which nitrogen is dissolved can be transferred to a crystal growth vessel (not shown) by the raw material transfer means 16. (Direction of arrow A). At one end of the gas introduction pipe 23, a gas supply device 21 is arranged via a flow rate regulator 22, and the other end is arranged so as to be positioned at the melt surface in the raw material preparation container 12. The nitrogen-containing gas can be supplied at the liquid level (in the direction of arrow B). By arranging a plurality of raw material preparation containers 12 in this manner, the gas-liquid boundary area where the melt and the nitrogen-containing gas come into contact can be increased. Further, by allowing the nitrogen-containing gas to flow on the surface of the melt, the nitrogen dissolution rate in the melt can be further increased.

 [0052] By using the manufacturing apparatus of Figs. 8, 9 and 10, the apparent growth rate can be increased, for example, to 1.5 to 2 times that of the conventional method.

 (Embodiment 6)

 Still another example of the configuration inside the second pressure vessel 52 will be described with reference to FIG. As shown in the figure, the raw material preparation container 12 is disposed in the second pressure container 52, and the heater 30 is disposed on a side surface thereof. A gas introduction pipe 23 and a raw material transfer means 16 are arranged in each raw material preparation vessel 12, and the melt (raw liquid) in which nitrogen is dissolved by the raw material transfer means 16 is supplied to a crystal growth vessel (see FIG. 1). (Not shown) (arrow A direction). A gas supply device 21 is arranged at one end of the gas introduction pipe 23 via a flow rate regulator 22, and the other end is arranged so as to penetrate a wall surface of the raw material preparation container 12. A nitrogen-containing gas is introduced into the raw material preparation container 12 through the gas introduction pipe 23. The transfer of the melt (raw material liquid) from the raw material preparation container to the crystal growth container can be performed, for example, by a pressure difference between the second pressure container and the first pressure container.

By arranging gas introduction pipe 23 in this manner, it is possible to publish a nitrogen-containing gas in the melt in raw material preparation container 12 and to dissolve nitrogen more quickly in the melt. be able to. Therefore, crystal growth can be started earlier. With the configuration of the present apparatus, when a GaN crystal is grown under the same conditions as in Embodiment 5, the time until the crystal growth starts can be set to, for example, less than 3 hours. As a result, the apparent crystal growth rate For example, compared to 2 to 2.5 times faster. In addition, since the inside of the raw material preparation container 12 is kept in an unsaturated state similarly to Embodiment 5 described above, the dissolution of nitrogen can be quickly realized. Further, microcrystals such as heterogeneous nucleation are not generated in the raw material preparation container 12.

 [0055] When publishing a nitrogen-containing gas, from the viewpoint of improving the dissolving efficiency of nitrogen in the melt, it is preferable to make bubbles stay in the melt as long as possible. For example, there is a method of reducing the size of bubbles by arranging a cap at the tip of the gas introduction tube. The method will be described with reference to FIG. FIG. 12 is a configuration diagram showing an example of the configuration of the peripheral part of the raw material preparation container 12, and the same reference numerals in FIG. 12 denote the same parts as in FIG. As shown in the figure, a gas introduction pipe 23 and a raw material transfer means 16 are arranged in the raw material preparation container 12 so as to penetrate the wall surface. A cap 27 is arranged at the tip of the gas introduction pipe 23. By supplying a nitrogen-containing gas into the melt through the cap 27 arranged at the tip of the gas introduction pipe 23, the size of the bubble is increased. Can be controlled (eg, reduced). By reducing the size of the bubble, the contact surface (gas-liquid interface area) between the melt and the nitrogen-containing gas can be increased. Further, by reducing the size of the bubble, the residence time of the bubble in the melt can be extended due to the viscosity of the melt and the influence of Brownian motion. As a result, since the dissolving efficiency of nitrogen in the melt can be improved, more nitrogen can be dissolved in the melt with a smaller gas flow rate. Therefore, even if the same amount of nitrogen is dissolved in the melt, a smaller gas flow rate is sufficient, so that evaporation of the alkali metal or alkaline earth metal in the melt can be further reduced. Furthermore, since the convection becomes relatively gentle by reducing the gas flow rate, even if the Group III element nitride crystal in the melt in the raw material preparation step becomes somewhat supersaturated, it is not uniform in the melt. There is also an effect that nuclei hardly occur.

[0056] The size of the bubble can be adjusted by, for example, the hole diameter of the cap 27, the flow rate of the supplied gas, and the like. To reduce the size of the bubble, for example, a cap having a small hole diameter is used. Good. For example, when the nitrogen-containing gas is supplied with the pore diameter of several xm to several hundred xm and the flow rate of 50 cc / min to 5000 cc / min, bubbles having a diameter of several μm to several hundred μm are supplied into the melt. it can. As the cap 27, for example, a porous alumina or the like And metal caps derived from porous ceramics, tungsten, tantalum, and the like.

As a method for allowing bubbles to stay in the melt for as long as possible, there is a method using ultrasonic waves in addition to or instead of the method of disposing a cap at the tip of the gas introduction tube. . The method will be described with reference to FIG. FIG. 13 is a configuration diagram showing another example of the configuration of the peripheral portion of the raw material preparation container. In FIG. 13, the same reference numerals are given to the same portions as in FIG. As shown in the figure, a raw material transfer means 16 is disposed on the right wall surface of the raw material preparation container 12 in a state penetrating the wall surface, and a lower part of the raw material preparation container 12 is connected to An ultrasonic generator 29 is arranged. A gas introduction tube 23 is arranged from the upper side of the material preparation container 12 such that the tip is located on the bottom surface of the material preparation container 12, and a cap 27 is arranged at the tip of the gas introduction tube 23. . By applying ultrasonic waves to the melt in the raw material preparation container 12 using the ultrasonic generator 29, the bubbles supplied from the gas introduction pipe 23 are fixed at, for example, the positions of the nodes of the ultrasonic waves. . As a result, bubbles can be kept in the melt for a longer time, and the dissolving efficiency of nitrogen can be further improved.

(Embodiment 7)

 In the present embodiment, still another example of the configuration of the manufacturing apparatus of the present invention will be described with reference to FIG. This example is a container in which a raw material preparation container and a crystal growth container are integrated, and has a double structure in which one container is divided into a raw material preparation container portion and a crystal growth container portion. In the figure, the same parts as those in FIG. 8 are denoted by the same reference numerals. As shown in the figure, this device has a pressure vessel 53, a pressure regulator 24, a flow regulator 22 and a gas supply device 21 as main components. The pressure vessel 53 can house a raw material preparation vessel and a crystal growth vessel 15, and a heater 30 is arranged on the side and bottom of the vessel 15. A flow regulator 22 and a pressure regulator 24 are connected to the pressure vessel 53 via pipes, respectively, and a gas supply device 21 is connected to the flow regulator 22 via pipes.

FIG. 15 shows an example of the configuration of the raw material preparation container and the crystal growth container 15. As shown in the figure, the upper part of the raw material preparation container / crystal growth container 15 can be closed by a lid 44. The inside of the raw material preparation container and crystal growth container 15 is separated by a partition plate 43 into a crystal growth container. It has a double structure divided into a part 46 and a raw material preparation container part 47, and a seed crystal 45 can be arranged in the crystal growth container part 46. Holes 42 are formed in the lower part of the partition plate 43 (near the bottom surface of the raw material preparation container and the crystal growth container 15) so that the melt in the raw material preparation container portion 47 can be transferred to the crystal growth container portion 46. . The gas introduction pipe 23 is disposed in the raw material preparation container part 47 so that the tip thereof is located at a lower portion (near the bottom surface of the raw material preparation container / crystal growth container 15). In addition, holes 48 and 49 are formed in the lid 44 so as to correspond to the raw material preparation container part 47 and the crystal growth container part 46, respectively. Nitrogen-containing gas and the like can be discharged. The hole 49 formed in the lid 44 of the crystal growth vessel section 46 is for making the pressure of the pressure vessel 53 and the pressure of the crystal growth vessel section 46 uniform.

The production of a group III element nitride crystal using the apparatus shown in FIGS. 14 and 15 will be described below. In advance, at least one of an alkali metal and an alkaline earth metal and a Group III element are arranged in a raw material preparation container and a crystal growth container 15. The raw material preparation container and the crystal growth container 15 are heated under pressure using the heater 30 and the pressure regulator 24 to prepare a melt containing at least one of an alkali metal and an alkaline earth metal and a Group III element. At this time, the temperature of the raw material preparation container part 47 is, for example, several degrees C to several tens of degrees higher than the temperature of the crystal growth container part 46. C Set to be high. Next, by bubbling a nitrogen-containing gas through the gas introduction pipe 23, nitrogen is dissolved in the melt in the melt in the raw material preparation container unit 47 to prepare a raw material liquid. The nitrogen-containing melt (raw material liquid) in the raw material preparation container part 47 diffuses into the crystal growth container part 46 through the holes 42 due to an increase in the nitrogen concentration of the melt in the raw material preparation container part 47 and publishing. . In this example, the holes 42 serve as the raw material transfer means. As described above, since the temperature of the crystal growth container 46 is lower than the temperature of the raw material preparation container 47, the melt containing nitrogen becomes supersaturated, and crystal growth starts on the surface of the seed crystal 45. As described above, by using the raw material preparation container part 47 and the crystal growth container part 46 as one container, the apparatus can be made compact and the transfer of the melt becomes extremely easy. Further, by transferring a melt (raw material solution) containing high-concentration nitrogen from the lower side of the crystal growth vessel section 46, nitrogen at the interface between the melt and the partition plate 43, the liquid level of the melt, and the like can be obtained. The concentration can be reduced, and as a result, the generation of heterogeneous nuclei can be further reduced. . In the present embodiment, the seed crystal 45 is arranged in an upright state. However, the present invention is not limited to this. The seed crystal 45 may be arranged on the bottom surface of the crystal growth vessel 46 with the seed crystal 45 laid down. The seed crystal 45 may be arranged diagonally.

Hereinafter, the group III element nitride semiconductor device of the present invention will be described with reference to examples.

 Example 1

 A semiconductor laser was manufactured using the crystal manufactured by the method of the present invention as a substrate. FIG. 16 shows the structure of the semiconductor laser 90.

First, a GaN crystal produced in the same manner as in the first embodiment is used as a substrate 91, and a carrier concentration of 5 × 10 ¹⁸ cm− ³ or less (for example, 0.7 × 10 An n-type GaN layer 92 to which Si was added as a dopant was formed to a thickness of ¹⁸ cm- ³ ). In GaN-based crystals (crystals containing Ga and N), when Si is added as a dopant, Ga vacancies tend to increase. Since the Ga vacancies are easily diffused, fabrication of a device on the Ga vacancies adversely affects the life and the like. Therefore, the amount of dopant was controlled so that the carrier concentration was 5 × 10 ¹⁸ cm− ³ or less, and a highly reliable device was fabricated.

 Next, on the n-type GaN layer 92, a cladding layer 93 having an n-type AlGaN force and a light guide layer 94 having an n-type GaN force were formed. Next, a well layer (about 3 nm thick) consisting of Ga In N and Ga

A multiple quantum well (MQW) constituted by an N barrier layer (thickness: 6 nm) was formed as the active layer 95. Then, an optical guide layer 96 made of p-type GaN, a cladding layer 97 made of p-type AlGaN, and a contact layer 98 made of p-type GaN were formed. These layers can be formed by a known method (for example, MOCVD method). The semiconductor laser 90 is a double heterojunction semiconductor laser. The energy gap of the well layer containing indium in the MQW active layer is smaller than the energy gap of the n-type and p-type cladding layers containing aluminum. On the other hand, the refractive index of the light was smaller than the largest in the well layer of the active layer 95, and was smaller in the order of the light guide layer and the cladding layer.

An insulating film 99 forming a current injection region having a width of about 2 μm was formed on the contact layer 98. A ridge portion serving as a current confinement portion was formed on the p-type cladding layer 97 and the p-type contact layer 98. Above the p-type contact layer 98, the contact layer 98 A P-side electrode 100 was formed to make contact. On the n-type GaN substrate 91, an n-side electrode 101 was formed which was in ohmic contact with the n-type GaN substrate 91.

 The device evaluation of the semiconductor laser manufactured by the above method was performed. As a result, when a predetermined forward voltage is applied between the p-side electrode and the n-type electrode to the obtained semiconductor laser, the MQW active layer has holes from the p-side electrode and holes from the n-side electrode. The electrons were injected and recombined in the MQW active layer to produce an optical gain, which caused laser oscillation at an oscillation wavelength of 404 nm. The GaN crystal obtained by the manufacturing method of the present invention has a low defect density and thus has high reliability.

 In this example, a semiconductor device was manufactured using a GaN single-crystal substrate. However, it is desirable to supply a substrate that absorbs less with respect to the operating wavelength of an optical device manufactured on the substrate. Therefore, as a substrate for semiconductor lasers and light emitting diodes in the ultraviolet region, it is necessary to form Al Ga Ν (0≤χ≤1) single crystals that contain a large amount of A1 and have low light absorption in the short wavelength region.

 1

 Is preferred. In the present invention, such a group III element nitride crystal can be formed by replacing a part of Ga with another group III element.

 Industrial applicability

As described above, according to the present invention, a crystal growth time can be reduced, and a high-quality and low-cost substrate can be provided. In addition, the GaN single-crystal substrate obtained by the manufacturing method and the manufacturing apparatus of the present invention has a lower dislocation density than a substrate manufactured by vapor phase growth (for example, HVPE) or the like. This is extremely advantageous for the production.

Claims

The scope of the claims

 [1] In a raw material liquid containing at least one of an alkali metal and an alkaline earth metal, a m-group element, and nitrogen, nitrogen and a m-group element in the raw material liquid are heated under pressure under a nitrogen-containing gas atmosphere. A method for producing a group III element nitride crystal having a crystal growth step of reacting and growing a crystal, comprising a raw material preparation step prior to the crystal growth step, wherein the raw material preparation step includes a nitrogen-containing gas. Under an atmosphere, at least one of the atmosphere temperature and the atmosphere pressure is set higher than the condition of the crystal growth step, and nitrogen is contained in the melt containing at least one of the alkali metal and the alkaline earth metal and the m group element. Is a process for preparing the raw material liquid by dissolving

 2. The production method according to claim 1, wherein, after switching from the raw material preparation step to the crystal growth step, a predetermined crystal growth temperature is set by gradually lowering an ambient temperature in the crystal growth step.

 [3] The method according to claim 2, wherein the rate of decrease in the ambient temperature is set in a range of 0.05 ° C / hour to 30 ° C / hour.

[4] After switching from the raw material preparation step to the crystal growth step, a predetermined crystal growth pressure is set by gradually increasing an atmospheric pressure in the crystal growth step.

The production method according to 1.

 [5] The rise rate of the atmospheric pressure is set to a value within a range from 0.3 Olatm / hour to 0.3 atm / hour (0.01 X 1.01

^5. The production method according to claim 4, wherein the temperature is set in a range of 3 X 10 ⁵ Pa / hour to 0.3 X 1.013 X 10 ⁵ Pa / hour).

[6] In the raw material preparation step, it sets its ambient temperature in the range of 800 ° C~1100 ° C, the atmospheric pressure 2atm~100atm (2 X l 013 X 10 5 Pa~:. 100 X 1. 013 set in the range of X 10 ⁵ P a), in the crystal growth process, to set the ambient temperature in the range of 600 ° C~1000 ° C, 2atm~ the ambient pressure:. 100atm (2 X l 013 X 10 ⁵ Pa~: 10 OX 1. the process according to claim 1, wherein the set X 10 ⁵ Pa) 013.

 7. The production method according to claim 1, wherein, in the raw material preparation step, the raw material liquid is in an unsaturated state of the group III element nitride crystal.

[8] The nitrogen-containing gas is caused to flow on the liquid surface of the melt in the raw material preparation step. The production method according to claim 1.

9. The production method according to claim 1, wherein in the raw material preparation step, the nitrogen-containing gas is bubbled in the melt.

10. The production method according to claim 1, wherein in the raw material preparation step, the nitrogen-containing gas in microbubbles is bubbled in the melt.

11. The method according to claim 9, wherein in the raw material preparation step, ultrasonic waves are applied to the melt.

 12. The production method according to claim 1, wherein the raw material preparation step is performed before or during the crystal growth step and / or during or after the crystal growth step.

 [13] In the crystal growth step, crystal growth is performed in a crystal growth vessel, and in the raw material preparation step, at least one of the alkali metal and the alkaline earth metal and a group III element are contained in the raw material preparation vessel. The production method according to claim 1, wherein a raw material liquid is prepared by dissolving nitrogen in the melt, and the raw material liquid is transferred from the raw material preparation container to the crystal growth container, where the crystal is grown.

 14. The method according to claim 13, wherein the raw material preparation container and the crystal growth container are integrated.

 15. The production method according to claim 1, wherein the group III element is at least one selected from the group consisting of Al, Ga, and In.

[16] The group III element is Ga, and the group III element nitride crystal is a GaN crystal.

 The production method according to 1.

[17] An apparatus for producing a Group IV element nitride crystal, comprising a heating means, a pressurizing means, a nitrogen-containing gas supply means, a crystal growth vessel, a raw material preparation vessel and a raw material transfer means, The raw material preparation container is connected via the raw material transfer means, and the crystal growth container and the raw material preparation container are respectively provided with the heating means, the pressurizing means, and the nitrogen-containing gas supply means. Then, the inside of the raw material preparation container is heated under pressure in a nitrogen-containing gas atmosphere by the heating means, the pressurizing means, and the nitrogen-containing gas supply means. And a melt containing at least one of an alkaline earth metal and nitrogen in the melt. The raw material liquid is prepared by dissolving the raw material. The raw material liquid is transferred from the raw material preparation container to the crystal growth container by the raw material transfer means, and the inside of the crystal growth container is heated by the heating means and the heating unit. Pressure means and the nitrogen-containing gas supply means, pressurizing and heating under a nitrogen-containing gas atmosphere to cause the nitrogen in the raw material liquid to react with the group III element, thereby growing a group III element nitride crystal. A production apparatus in which at least one of the ambient temperature and the atmospheric pressure in the raw material preparation container is set higher than the crystal growth container.

 [18] The apparatus further includes a first pressure vessel and a second pressure vessel, wherein the crystal growth vessel is disposed in the first pressure vessel, and the crystal growth vessel is disposed in the second pressure vessel. 18. The production apparatus according to claim 17, wherein a raw material preparation container is arranged.

 [19] The manufacturing apparatus according to claim 17, further comprising at least one of a temperature adjusting unit and a pressure adjusting unit.

 [20] The production apparatus according to claim 17, further comprising gas flow means, whereby the nitrogen-containing gas can be caused to flow on the melt surface of the raw material preparation container.

[21] The production apparatus according to claim 17, comprising a plurality of the raw material preparation containers, thereby increasing an area of contact between the melt of the raw material preparation container and the nitrogen-containing gas.

22. The production apparatus according to claim 17, further comprising gas publishing means, whereby the nitrogen-containing gas can be published in the melt of the raw material preparation container.

 23. The production apparatus according to claim 22, wherein the gas publishing unit can publish a microbubble nitrogen-containing gas in the melt of the raw material preparation container.

24. The production apparatus according to claim 22, further comprising an ultrasonic generator, wherein the ultrasonic generator is disposed in the raw material preparation container.

25. The production apparatus according to claim 17, further comprising a stirring means, whereby the melt can be stirred in the melt in the raw material preparation container.

[26] The raw material preparation container and the crystal growth container include a raw material preparation container and a crystal growth container in which the raw material preparation container and the crystal growth container are integrated. Divided into a raw material preparation container part and a crystal growth container part, 18. The production apparatus according to claim 17, wherein a through hole is formed between the raw material preparation container portion and the crystal growth container portion as the transfer means, and the raw material is transferred by the through hole.

[27] A group III element nitride semiconductor device including a crystal obtained by the production method according to claim 1.

[28] The group III element nitride semiconductor device according to claim 27, which is a light emitting device.